"vireye" the G30 has a capacity of 10 .45 ACP, vs the P228's 13 or 9mm. It's a pretty negligible difference (I never liked that small capacity for a 9mm....) and it's still more than a 1911!
Or....you could sell the glock (or Sig) and pick up a Springfield XDm in .45. If you get the full size it's 13+1 of .45 caliber goodness.
If you opt for the 3.8" compact model it's 9+1, and you can carry 13 round backup mags with grip extensions slid on. I have this in a 9mm model and it works great. I bought a pinky extension for the standard mag which really helps with grip, and carry a full size backup mag with the grip sleave.